<h2>memory_object_data_request</h2>
<hr>
<p>
<strong>Server Interface</strong> - Request that memory manager page-in specified data.
<h3>SYNOPSIS</h3>
<pre>
<strong>kern_return_t   memory_object_data_request</strong>
                <strong>(memory_object_t</strong>                  <var>memory_object</var>,
                 <strong>memory_object_control_t</strong>         <var>memory_control</var>,
                 <strong>vm_offset_t</strong>                             <var>offset</var>,
                 <strong>vm_size_t</strong>                               <var>length</var>,
                 <strong>vm_prot_t</strong>                       <var>desired_access</var><strong>);</strong>


<strong>kern_return_t   seqnos_memory_object_data_request</strong>
                <strong>(memory_object_t</strong>                  <var>memory_object</var>,
                 <strong>mach_port_seqno_t</strong>                        <var>seqno</var>,
                 <strong>memory_object_control_t</strong>         <var>memory_control</var>,
                 <strong>vm_offset_t</strong>                             <var>offset</var>,
                 <strong>vm_size_t</strong>                               <var>length</var>,
                 <strong>vm_prot_t</strong>                       <var>desired_access</var><strong>);</strong>
</pre>
<h3>PARAMETERS</h3>
<dl>
<p>
<dt> <var>memory_object</var> 
<dd>
[in abstract-memory-object (receive) right]
The abstract memory
object port that represents the memory object data.
<p>
<dt> <var>seqno</var> 
<dd>
[in scalar]
The sequence number of this message relative to the abstract 
memory object port.
<p>
<dt> <var>memory_control</var> 
<dd>
[in memory-cache-control send right]
The memory cache control port 
to be used for a response by the memory manager.  If the memory
object has been supplied to more than one kernel, this parameter
identifies the kernel that is making the call.
<p>
<dt> <var>offset</var> 
<dd>
[in scalar]
The offset within the memory object.
<p>
<dt> <var>length</var> 
<dd>
[in scalar]
The number of bytes requested, starting at <var>offset</var>.  The
number converts to an integral number of virtual pages.
<p>
<dt> <var>desired_access</var> 
<dd>
[in scalar]
The memory access modes to be allowed for the cached 
data.  Possible values are obtained by or'ing together the following
values:
<dl>
<p>
<dt> <strong>VM_PROT_READ</strong>
<dd>
Allows read access.
<p>
<dt> <strong>VM_PROT_WRITE</strong>
<dd>
Allows write access.
<p>
<dt> <strong>VM_PROT_EXECUTE</strong>
<dd>
Allows execute access.
</dl>
</dl>
<h3>DESCRIPTION</h3>
<p>
A <strong>memory_object_data_request</strong> function is called as
the result of a kernel 
message requesting data from the specified memory object, for at least the
access specified.
<p>
The kernel issues this call after a cache miss (that is, a page
fault for which the 
kernel does not have the data).  The kernel requests only amounts
of data that are 
multiples of the page size included in the
<strong>memory_object_init</strong> or <strong>memory_object_create</strong> call.
<p>
The memory manager is expected to use <strong>memory_object_data_supply</strong> to
return at least the specified data, with as much access as it
can allow.  If the
memory manager cannot provide the data (for example, because
of a hardware error), 
it can use the <strong>memory_object_data_error</strong> call.  The
memory manager can also 
use <strong>memory_object_data_unavailable</strong> to tell the kernel
to supply zero-filled 
memory for the region.
<h3>RETURN VALUES</h3>
<p>
Only generic errors apply.
<h3>RELATED INFORMATION</h3>
<p>
Functions:
<a href="memory_object_data_error.html"><strong>memory_object_data_error</strong></a>,
<a href="memory_object_data_supply.html"><strong>memory_object_data_supply</strong></a>,
<a href="MO_data_unavailable.html"><strong>memory_object_data_unavailable</strong></a>,
<a href="memory_object_server.html"><strong>memory_object_server</strong></a>,
<a href="SMO_server.html"><strong>seqnos_memory_object_server</strong></a>.

